Local area networks such as Ethernet are well known. Most local area networks are wired, so that each station is coupled directly or indirectly to all other stations by cabling or wires, thus providing full connectivity between all stations. Such local area networks avoid collisions and achieve efficient use of the communications channel by well known carrier sensing and collision avoidance schemes. Such schemes are typically not suitable for wireless networks. Communication systems that utilize coded communication signals are well known in the art. One such system is a code division multiple access (CDMA) cellular communication system such as the one set forth in the Telecommunications Industry Association/Electronic Industries Association International Standard (TIA/EIA IS-95), hereinafter referred to as IS-95.
In accordance with the IS-95, the coded communication signals used in CDMA systems comprise CDMA signals that are transmitted in a common 1.25 MHz bandwidth. The signals may be communicated to base stations of the system from mobile or wireless communication units, such as cell phones, or portable wireless computers, and wireless handheld devices that are communicating in a specific coverage area of the base station. In conventional CDMA systems, the base station communicates with a base station controller (BSC) that allows each communication unit to communicate with other communication units within the same coverage area. Each CDMA signal includes a pseudo-noise (PN) sequence associated with a particular base station and an identification number of a communicating communication unit.
Typically, the BSC is coupled to a mobile switching controller (MSC). This allows a base station to connect with other base stations outside its coverage area in order to allow a communicating communication unit to communicate with other units outside its coverage area.
FIG. 1 is an illustration of a conventional prior art CDMA system. In the system shown in FIG. 1, base stations 110 and 120 are coupled to a BSC 130 and a MSC 140. MSC 140 is in turn coupled to the public switched telephone network (PSTN) 150 using known techniques.
In the system shown in FIG. 1, when a communication unit initiates a call sequence to either one of the base stations 110 and 120 within a coverage area, an end-to-end connection is established between the respective base stations, the BSC 130 and the MSC 140 using known CDMA call setup techniques. The base stations 110 and 120 typically communicate with the BSC 130 and the MSC 140 via communication links, such as a T1 connection. Base stations 110 and 120 typically have antennas to define the coverage area within which either base stations primarily accommodate the communication units.
With the proliferation of wireless devices in the office and school environment, the communication system shown in FIG. 1 can be very expensive if implemented in an office or in-building environment. The system in FIG. 1 also has the inherent problem of wireless voice and data signal quality degradation if implemented in an in-building environment.
To alleviate the problems of the system shown in FIG. 1 and with the advent of enterprise based wireless networks, some prior art CDMA systems implement the system shown in FIG. 2. In the system illustrated in FIG. 2, a wireless base station is coupled to existing ethernet network infrastructure to enable the CDMA system to utilize existing internet protocol techniques to allow communication between wireless devices coupled to the ethernet network.
The system in FIG. 2 utilizes a combination of wireless signaling protocol and media gateway protocol to allow wireless call handling and other multi-media data transmission. A wireless signaling protocol may be used to handle mobile terminals.
Despite the robustness of the system in FIG. 2, an in-building wireless environment, there are some disadvantages which characterize such a system. First, the system in FIG. 2 uses a combination of wireless signaling protocol and media gateway control protocol (MGCP). A wireless signaling protocol may be used to handle mobile terminals and current MGCP protocol assumes that the mobile terminal is wired (at least fixed for the duration of a call). Hence, mobile terminal signaling cannot be sufficiently processed using MGCP protocol alone.
Second, the system uses two different protocols to handle wireless voice communication and other media communication. Whereas a signaling gateway can handle wireless communication, a media gateway cannot handle typical wireless functions, such as location registration of a mobile terminal, paging a mobile terminal, and processing handoff of mobile terminals from one base station to another during a conversation in the MGCP protocol.
Thus, the system in FIG. 2 requires the base station to have two functional protocol units to handle wireless signaling and multi-media transactions. Traditionally in the wireless network, an open interface specification is defined between base stations and an MSC. The MSC is a Call Agent-like entity that can handle the mobile terminal signaling. In CDMA wireless network, the TIA/EIA-634 specification defines the interface.
On the other hand, TIA/EIA-634 specification does not define the media control of the Internet protocol local access network (IP LAN). Because the TIA/EIA-634 specification assumes a circuit-based network, the media identifier is specified in terms of TDM circuit ID of a trunk line between a base station and the MSC. Thus, the wireless signaling protocol is also not sufficient to control the packet based media stream on an IP LAN.
In order to handle both wireless mobile terminal signaling and also media traffic of the wireless mobile terminal, it is necessary for the system in FIG. 2 to support both wireless signaling protocol as well as IP media control protocol. For example, in a CDMA network, TIA/EIA-634 and MGCP can be used for such purpose.
In the example illustrated in FIG. 2, protocol interfaces used between a Call Agent and a base station are based on a packet-based IP LAN. A problem typically arises when the wireless signaling protocol and the MGCP are used together between a Call Agent and a base station. A linkage (or mapping) between a call identifier in the wireless signaling protocol and a call identifier of the corresponding call for the same mobile terminal must be made dynamically during each call setup. Because mobile terminals tend to move around within a particular call coverage area, a static system mapping of call identifiers for a given terminal by a base station is not economically feasible.
Furthermore, TLA/EIA-634 protocol does not have a method to specify the traffic path on an IP LAN associated with a particular signaling call that it is handling. In a conventional circuit based network, TIA/EIA-634 uses 16 bit identification typically known as Circuit Identity Code (CIC) which defines a PCM multiplexer ID to handle traffic path for a signaling call associated with it. However, this is not adequate for the traffic path on an IP LAN because the PCM multiplexer is not present on IP LANs and MGCP does not have any method to associate the mobile terminal to the connection. Since MGCP typically deals with the fixed connection, MGCP does not describe mobile endpoints to set up the traffic connections to a call.
Thus, it is desirable to have a system and a method for transmitting CDMA calls including voice and data over a communication pathway with a higher bandwidth. It is further desirable to have a CDMA system that handles the transmission of calls, especially data calls, without the inherent difficulties of using a variety of transmission protocols for the same call. A need further exists for an improved and less costly system which improves efficiency, transmission rate, and time of calls between a mobile unit and a base station, between base stations and a BSC, and between adjacent base stations.